Need Help With A Stacked Suitcase Cake Please

I have an order in February for a stacked suitcase cake. I know that I can decorate it no problem but I need a little help with the cake sizes. I always struggle with serving sizes because I am still pretty new and don't have a go to chart. I need a cake that will serve 90 - 100. It will be 3 tiers and I was planning on the bottom tier being 11x15 - 4", the middle tier 7 1/2x11 - 4" and the top tier is a 6" round. According to the Wilton I believe that will give me 102 servings? The client provided a picture of what they like, I have changed the design but this is the look they are going for. My question is will these cake sizes achieve this look and provide the right amount of servings? Any help is appreciated please :) Thank you!

AI don't have a calculator or a chart, but I figured up more like 124. That doesnt include the extra servings on the side of the rectangles which would add about 10-15 more servings. Maybe this will give you a bump and somebody will have a definite number. Because I thought I remembered that my chart says the 11x15 is 68 servings, so idk.

Thank you Howsweet! It always helps to have reassurance...I am always so worried I am not going to provide enough servings. I have found a few threads and the answers vary so much. I am going to say the bottom tier is about 60 servings the middle is half that at 30 and the top is 10. I think it is actually more than that but I am pretty sure that it will be at least 100 good size party servings.

I am also wondering about how those sizes will look stacked? Will they achieve the same look as the picture provided?